Sister chromatid swap

Sister chromatid exchange is a new method in cytogenetics research in recent years. The principle is that when cells are contacted with 5-bromodeoxyuracil nucleoside (Brdu), Brdu can be used as a nucleotide precursor to specifically replace thymine into the newly synthesized DNA strand. As long as two cell replication cycles are passed, one of the DNA double strands of the sister chromatid can be incorporated with Brdu, and the other DNA double stranded with two strands Cells fully incorporated with Brdu. After differentiation and staining, you can see that there are obvious differences between the two sister chromatids on the same chromosome, one of which is dark and the other is light.